This invention relates in general to fixtures for mounting vehicle wheels on machine tools during finishing operations and in particular to a fixture for mounting a vehicle wheel on a lathe while the exterior surface of the wheel rim is turned to its final shape.
Light weight alloy vehicle wheels are becoming increasingly popular. Such wheels typically include an annular wheel rim which carries a tire. The wheel rim has a recessed center portion which facilitates mounting the tire upon the rim. The ends of the wheel rim include inboard and outboard tire bead seats which support the tire. Inboard and outboard tire bead retaining flanges are formed on the ends of the wheel rim to retain the tire upon the wheel rim.
A circular wheel disc is formed across one end of the wheel rim. The wheel disc usually includes a central hub portion supported within the wheel rim by a plurality of wheel spokes. A central pilot hole and plurality of wheel mounting holes are formed through the wheel hub. The mounting holes are drilled equally spaced about a circle which is concentric with the pilot hole. The central pilot hole is used to position the wheel on a vehicle and the mounting holes are used to secure the wheel to the vehicle.
One conventional process for manufacturing light weight alloy wheels involves pouring molten metal into a wheel mold to form a casting of the wheel. After the molten metal solidifies, the wheel casting is removed from the mold. The wheel casting is oversized and is machined to final shape with machining operations.
Finishing the wheel casting typically includes multiple machining operations. Sawing machines cut any casting gates and risers from the wheel casting. A drilling machine is used to drill the central pilot hole and the wheel mounting holes through the wheel hub. The wheel casting is mounted upon a lathe for machining to its final shape. During the lathe operations, the inside surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel hub surface is faced and both the inside and outside of the wheel rim are turned to their final shapes. During the finishing of the outside of the wheel rim, the tire bead seats are turned to their final diameter. Additionally, portions of the wheel can be painted or covered with a clear coating to protect the wheel from corrosion and/or enhance its appearance.
The machining operations are carried out with highly automated machining stations, which usually include numerically controlled machine tools designed to complete one or more specific machining operations. The wheels are sequentially moved between the machining stations, with the machine tool located at each station completing a portion of the required machining. For example, a typical wheel production facility can include multiple lathe stations. The lathe stations can include one lathe for facing the inboard wheel hub surface, a second lathe for facing the outboard wheel disc surface, a third lathe to turn the inside surface of the wheel rim and a fourth lathe to turn the outside surface of the wheel rim. Alternately, a special lathe can be designed to perform more than one of the above operations at a single machining station. Mounting fixtures are typically designed for each machine tool to facilitate mounting and demounting the wheels on the tool.